Rogue Trader Revised Area Fire Procedure
The Rogue Trader rules for area effect weapons were replaced in White Dwarf 99. They are presented here for your edification.
Rogue Trader remains in print. The supporting materials are harder to get your hands on.
One of the most common questions about the WH40K rules concerns the procedure for area fire, especially with regard to deviation. In my Marginalia article for WH40K, I confessed that even I wasn't entirely happy with the system. To summarise briefly - the procedure as given in the book is: 1) place your area marker; 2) roll for deviation using the area marker size deviation number; 3) roll 'to hit' each target withing the area using the firer's BS; 4) roll 'to wound/damage' on any hits; 5) take saving throws.
-Rick Priestly, White Dwarf 99 (1988)
Revised Area Fire Procedure
1. Place area marker over target as normal.
2. Roll to see if the shot lands on target or 'deviates'. The chance of a shot deviating is now based on BS, not the size of the template. This directly reflects the chance of the firer landing his grenade or mortar bomb on target.
| BS | Deviates on D6 score of |
|---|---|
| 1 | 1 or more (always deviates) |
| 2 | 2 or more |
| 3 | 3 or more |
| 4 | 4 or more |
| 5 | 5 or more |
| 6+ | 6 or more (minimum chance of deviation) |
Any weapon 'to hit' modifier may be added to the BS of the firer. No other modifiers apply. Shots which don't deviate are worked out with the area marker remaining as placed. If a shot deviates, the missile, grenades etc, land slightly off-target. The procedure for establishing deviation remains the same: roll a D12 for direction and an appropriate dice for distance.
3. Models within the area marker may be hit by the blast of the weapon. Any model will be hit on a D6 score of 3 or more. Basic 'to hit' dice modifiers apply (see p20 of the WH40K rule book). Weapon modifiers do not apply. Note that some weapons still hit automatically as defined in the rules.
4. Establish whether hits cause wound/damage, take any saves, roll for the number of wounds/damage where appropriate and remove casualties as normal.
Battle Manual
Along with a plethora of other changes the Battle Manual replaced these rules with a scatter die based approach. This included a misfire table that could destroy the weapon or even kill the model.
This is closer to but still more complicated than the 2nd edition rules which introduced a dedicated artillery die.